import pygame
from pygame.sprite import Sprite

class Ailen(Sprite):

    def __init__(self,ai_settings,screen):
        #属性
        super().__init__()
        self.screen = screen
        self.ai_settings = ai_settings
        #关联图片
        self.image= pygame.image.load("images/alien.bmp")
        self.rect = self.image.get_rect()

        #图片位置的初始化
        self.rect.x = self.rect.width
        self.rect.y = self.rect.height
        #移动增加的x
        self.x = float(self.rect.x)
        self.alien_speed_factor = ai_settings.alien_speed_factor
    #检查是否到屏幕边缘
    def check_edges(self):
        screen_rect =  self.screen.get_rect()
        if self.rect.right >= screen_rect.right:
            return True
        elif self.rect.left <= 0:
            return True
    #移动方法
    def update(self):
        #巧妙
        self.x = self.x+(self.alien_speed_factor*self.ai_settings.feet_direction)
        self.rect.x = self.x

    #在屏幕上画出外星人
    def blitme(self):
        self.screen.blit(self.image,self.rect)